Various methods for performing a solid-liquid separation on treated water using a membrane module with a separation membrane such as a micro-filtration membrane or an ultra-filtration membrane disposed therein have been examined for water treatments such as water purification and sewage treatment. If a filtration treatment is performed on treated liquid using a separation film, it is possible to obtain a filtrate from which solid has been separated and removed to a high degree. Examples of a solid-liquid separation apparatus using such a membrane module include an apparatus in which a plurality of membrane modules, each of which includes a pair of housings for integrally fixing liquid-permeable hollow fiber arranged in a membrane shape such that both ends thereof are accommodated in the housings, are arranged in a dipping tank filled with treated liquid.
According to an apparatus configured such that the housings of each module are connected to a water collecting header via a connecting member and a suctioning apparatus is connected to the water collecting header for suction, filtrate from which solid contained in the treated liquid has been separated and removed on the surface of respective hollow fiber passes through the hollow fiber, is introduced into the housings, collected in the water collecting header via the connecting member, and discharged outside the dipping tank.
If the membrane module and the membrane module unit are increased in size in order to increase a treatment quantity in the solid-liquid separation apparatus using this type of membrane module, the diameter of a filtrate outlet port is increased, and the liquid collecting header is also increased in size in accordance with a quantity of flowing filtrate. On the other hand, the membrane module is required to be compact while also required to enhance the treatment quantity, and therefore, the thickness of the membrane module is designed to be as thin as possible. For this reason, the diameter of the filtrate outlet port is also decreased. Furthermore, in many cases it is possible for one outlet port alone to cause filtrate to smoothly flow, and in such cases, a plurality of filtrate outlet ports are provided in one membrane module.
It is difficult to directly couple the membrane module and the water collecting header, which have been increased in size, due to variations in the dimensions of respective members thereof. Thus, Patent Literatures 1 and 2 have proposed a solid-liquid separation apparatus, a membrane module unit, and a connecting member which are light, compact, and inexpensive while being capable of absorbing a dimension error, in which the connecting member, a housing of a membrane module, and a liquid collecting header can be easily and reliably connected to each other in a slidable and liquid-tight manner, wear and damage are suppressed at a connecting part between the housing of the membrane module or the water collecting header and the connecting member even when the part is influenced by vibration of the membrane module for dispersing solid adhered on the surface of the hollow fiber over a long period, and a solid-liquid separation treatment can be stably performed over a long period.